146 AMERICAN MARINE CONCHOLOGY. 
Spurious Species. 
Mactra nucleus, Conrad. This species, described from two odd 
valves stated to have been collected at Long Branch, N. J., is now 
ascertained to be a Manilla species. 
Genus RAETA, Gray. 
1. R. CANALIOULATA, Say. Fig. 343. 
Journ. Philad. Acad., ii. 311. 1822. 
Shell transversely oval orbicular, very thin and fragile, inflated; 
valves with equal concentric grooves; posterior margin short, 
subreniform, compressed ; a marginal longitudinal irregular sub- 
impressed line, between which and the edges the grooves become 
mere wrinkles; posterior slope nearly straight ; gape considerable ; 
anterior margin regularly curved ; within grooved. White. 
Length 2.5, height 2 inches. 
New Jersey, southwards. 
2. R. pingaTA, Say. Fig. 344. 
Journ. Philad. Acad., ii. 310. 1822. 
Shell transversely sub-oval, thin; posterior gap patulous; 
anterior linear, and commencing beyond the hinge slope; valves 
unequally obsoletely wrinkled; anterior margin smooth with a 
carinated line. White. 
Length 2.75, height 2 inches. 
New Jersey, southwards. 
Family TELLINIDA. 
Animal with the mantle widely open in front, its margins 
fringed; foot tongue-shaped, compressed; siphons separate, 
_ generally very long and slender; palpi large, triangular; gills 
united posteriorly, unequal, the outer pair sometimes directed 
dorsally. 
The shell is free, compressed, usually closed and equivalve; 
cardinal teeth two at most, laterals 1-1, sometimes obsolete; 
muscular impressions rounded, polished; pallial sinus very large; 
ligament on the shortest side of the shell. 
The Tellens are found in all seas, chiefly in the littoral and 
laminarian zones ; they frequent sandy nee y or sandy mud, 
burying beneath the surface. 
